将 Cardinal 转换为 IUnknow
我现在正在致力于将 Visual Basic 代码采用到 Delphi 代码中。
我所拥有的：
// prepare query
with oleClipboardFormat do
begin
cfFormat := CF_FileContents;
ptd := nil;
dwAspect := DVASPECT_CONTENT;
lindex := Index;
tymed := TYMED_ISTREAM or TYMED_ISTORAGE;
end;
// query data
data.GetData(oleClipboardFormat, oleMedium)
字段oleMedium.hGlobal（变量类型为Cardinal）包含对IStorage接口的引用。
我应该如何将 oleMedium.hGlobal 转换为 IStorage？
我现在正在翻译的 VB 源代码中有某种黑魔法。代码的作者使用以下 Visual Basic 函数将指针转换为接口......
Private Function ResolvePointer(ByVal PtrObj As Long) As stdole.IUnknown
Dim oUnk As stdole.IUnknown
' Get an uncounted reference
' to the IUnknown interface
MoveMemory oUnk, PtrObj, 4&
' Get a counted reference
Set ResolvePointer = oUnk
' Release the uncounted reference
MoveMemory oUnk, 0&, 4&
End Function
I am working on adoption of Visual Basic code into Delphi code right now.
What I have:
// prepare query
with oleClipboardFormat do
begin
cfFormat := CF_FileContents;
ptd := nil;
dwAspect := DVASPECT_CONTENT;
lindex := Index;
tymed := TYMED_ISTREAM or TYMED_ISTORAGE;
end;
// query data
data.GetData(oleClipboardFormat, oleMedium)
The field oleMedium.hGlobal (type of variable is Cardinal) contains a reference to IStorage interface.
How should I cast oleMedium.hGlobal to IStorage?
There is some kind of black magic in the VB sources I am translating right now. The author of the code uses following visual basic function to cast pointers to interfaces...
Private Function ResolvePointer(ByVal PtrObj As Long) As stdole.IUnknown
Dim oUnk As stdole.IUnknown
' Get an uncounted reference
' to the IUnknown interface
MoveMemory oUnk, PtrObj, 4&
' Get a counted reference
Set ResolvePointer = oUnk
' Release the uncounted reference
MoveMemory oUnk, 0&, 4&
End Function
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您的
oleMedium变量被声明为TStgMedium。它有一个hGlobal字段，但它也有一个stg字段，其类型为Pointer。使用该字段，并在需要使用该接口时将其类型转换为IStorage：您的 VB 作者没有可供使用的类型转换，因此代码从一个变量复制内存到另一个。
Your
oleMediumvariable is declared as aTStgMedium. It has anhGlobalfield, but it also has astgfield, which is of typePointer. Use that field, and type-cast it toIStoragewhen you need to use the interface:Your VB author didn't have type-casting at his or her disposal, so the code copied memory from one variable to another.